The invention relates to lifting devices, such as jacks, and particularly to fluid pressure or pneumatic type lifting devices.
The difficulties, dangers and general inconveniences which are characteristic of mechanical lifting devices or jacks are well known. Many mechanical jacks are multi-component structures which require assembling prior to use. Once in use, the stability of such jacks is often unsatisfactory, requiring the user to take added precautionary measures to guard against the vehicle or other structure being lifted from coming free of contact with and support by the jack. Furthermore, convenient and compact storage of these mechanical jacks is a problem due to their bulk, size and/or weight.
Alleviation of certain of the aforementioned problems attending mechanical jacks has been made possible with fluid pressure or pneumatic type jacks. One of the more commmon forms of pneumatic jacks are the barrel-shaped or cylindrical bag structures which operate on a bellows type principle. These pneumatic jacks, when compared with most known mechanical jacks, offer advantages of an essentially one-piece structure, easy and convenient storage, better stability and lighter weight. One disadvantage of these jacks, has been their high manufacturing cost, a factor believed to have precluded a wider acceptance in the market.
Although efforts have been made to develop pneumatic type jack designs requiring less expensive manufacturing costs, such designs have heretofore been incapable of significantly achieving the advantages over mechanical jacks which are characteristic of the aforementioned cylindrical or bellows-type pneumatic jacks.